Subtitle language filter does not include detected languages (e.g. Czech / cs)

[zafodtom]

Describe the feature you'd like

Add support for filtering scenes by all detected subtitle languages, including Czech (cs).

Subtitles with valid ISO 639-1 language codes (e.g. cs) are correctly detected and displayed in the scene player, but are not available as options in the Subtitle Language filter. The filter should allow selecting these detected languages.

Describe the benefits this would bring to existing users

Users would be able to reliably filter and organize scenes based on the actual subtitle languages they have available.

This improves library navigation, reduces manual tagging workarounds, and enables consistent subtitle-based filtering for non-English and less common languages, benefiting international users with multilingual collections.

Is there an existing way to achieve this goal?

Yes.

Currently, users can manually tag scenes (e.g. subtitles-cs) to simulate subtitle language filtering. However, this is a manual workaround that duplicates information already detected by Stash.

The proposed feature would provide native, automatic filtering based on detected subtitle metadata, removing the need for manual tags.

Have you searched for an existing open/closed issue?

• I have searched for existing issues and none cover the core request of my proposal

Additional context

Environment:

Stash version: v0.30.1

Installation: Docker

Subtitles: external .srt files using ISO 639-1 language codes (e.g. MovieName.cs.srt)

The issue is not limited to Czech and likely affects any valid language not included in the current subtitle filter list.